Tethered aminohydroxylation using acyclic homo-allylic sulfamate esters and sulfonamides as substrates

Article abstract of DOI:10.1039/b416477f

Homo-allylic sulfamate esters and sulfonamides are shown to be useful substrates for the tethered aminohydroxylation (TA) reaction. The sulfamate esters undergo the TA reaction delivering 1,2,3-oxathiazinane products whereas the sulfonamides give 1,2-thia

Full text of DOI:10.1039/b416477f

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A R T I C L E
Tethered aminohydroxylation using acyclic homo-allylic sulfamate
esters and sulfonamides as substrates
Martin N. Kenworthy* and Richard J. K. Taylor*
Department of Chemistry, University of York, Heslington, York, UK YO10 5DD.
E-mail: rjkt1@york.ac.uk; Fax: +44 (0) 1904 432523; Tel: +44 (0) 1904 432606
Received 27th October 2004, Accepted 30th November 2004
First published as an Advance Article on the web 11th January 2005
Homo-allylic sulfamate esters and sulfonamides are shown to be useful substrates for the tethered
aminohydroxylation (TA) reaction. The sulfamate esters undergo the TA reaction delivering 1,2,3-oxathiazinane
products whereas the sulfonamides give 1,2-thiazinane products. A range of acyclic homo-allylic sulfamate esters
were prepared and subjected to the TA reaction to establish the scope of the process. Nucleophilic ring-opening
reactions of the 1,2,3-oxathiazinane products are also described.
8c
8d
to be highly diastereoselective with both cyclic and acyclic
substrates.
Introduction
The vicinal amino alcohol unit is an important structural motif
found widely in compounds isolated from nature, and also
common in synthetic pharmaceuticals.1 The most important
uses of amino alcohols are as chiral building blocks, and
components of catalysts and auxiliaries employed in asymmetric
synthesis.1 Consequently, a wide range of methods have been
devised for their synthesis.1 A major milestone in the preparation
of these highly prized compounds came with the development
of the asymmetric aminohydroxylation (AA) by Sharpless and
co-workers.2 The reaction was an extension of the Sharpless
asymmetric dihydroxylation,3 employing an N-haloamine salt
as both the nitrogen source and stoichiometric oxidant, along
with an osmium(VI) catalyst.4 Addition of catalytic quantities
of cinchona-derived ligands (e.g. (DHQ)2PHAL) generally led
to products in high enantiomeric excess. Initial studies concen-
trated on cinnamyl5 and styrenyl6 olefinic substrates raising
regiochemistry questions. Although in some specific systems
high levels of regiocontrol are observed,7 the level of regiocontrol
Donohoe et al. also showed that the allylic/homo-allylic
carbamate 3 demonstrates not only the high acyclic diastere-
oselectivity achievable, but also the preference for the reaction
to proceed through a 5-membered ring-forming manifold in
preference to a 6-membered variant, giving 4 in good yield
8a,d
(Scheme 2).
Scheme 2 Reagents and conditions: (i) nPrOH–H2O, NaOH (0.92 eq.),
tBuOCl (1.0 eq.), EtN(iPr)2 (5 mol%), K2OsO4·2H2O (4 mol%).
a
Recovered starting material in parentheses.
2b
can be problematic.
An innovative solution to the regioselectivity problem was in-
troduced by Donohoe and co-workers; they connected together
the nitrogen source and the olefin in a reaction described as a
tethered aminohydroxylation (TA).8 The substrates employed
in this reaction were carbamates (e.g. 1), which are easily
obtained from the corresponding allylic alcohols. The reaction
proceeds by treatment of the allylic carbamate with NaOH and
tBuOCl to form an N-chloroamine salt. Subsequently, treatment
with catalytic potassium osmate(VI) and an amine ligand gave
the oxazolidine product 2 in a totally regiocontrolled manner
(Scheme 1). Although no enantioselectivity was observed when
We have recently used the TA reaction of the tertiary homo-
allylic carbamate 5, to prepare the TA product 6 which was used
to gain access to simplified analogues 7 of the naturally occur-
ring sphingomyelinase inhibitor, scyphostatin (Scheme 3).9 The
modest yield of the 6-membered ring carbamate 6 is consistent
with the relatively low efficiency observed by Donohoe’s group
8a
when forming 6-membered ring carbamates.
It has recently been reported that intramolecular C–H
insertion10,11 and aziridination12 reactions of sulfamate esters
8 and 12 and sulfonamide 10, in general, give excellent yields
of 1,2,3-oxathiazinane 9 and 13, and 1,2-thiazinane products
11 (Scheme 4). Moreover, in the case of C–H insertion re-
actions (Scheme 4a and b) the reactions actually proceeded
exclusively through the 6-membered ring manifold, only forming
5-membered rings when the 6-ring option was not possible.10 In
the case of the sulfamate ester 8, this behaviour was suggested
to be due to the elongated nature of S–O and S–N bonds, along
8b
Sharpless’ cinchona ligands were used, the reaction was found
10a
with the large bond angle of the N–S–O moiety.
The results in Scheme 4 suggested that it would be worthwhile
investigating whether sulfamate esters 14 and sulfonamides 16
can be employed as substrates in 6-membered ring-forming
TA reactions (Scheme 5), particularly with a view to possibly
increasing the efficiency of the process and broadening the range
of substrates which can be utilised in this reaction. Also, 1,2,3-
oxathiazinane products 15, obtained from the sulfamate esters
14, could then be useful for further elaboration by nucleophilic
ring-opening reactions,13 delivering b-functionalised amino al-
cohols 18.
Scheme 1 Reagents and conditions: (i) nPrOH–H2O, NaOH (0.92 eq.),
tBuOCl (1.0 eq.), EtN(iPr)2 (5 mol%), K2OsO4·2H2O (4 mol%).
a
Recovered starting material in parentheses.
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1
6 0 3
©

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Scheme 3 Reagents and conditions: (i) nPrOH–H2O, NaOH (0.92 eq.), tBuOCl (1.0 eq.), EtN(iPr)2 (5 mol%), K2OsO4·2H2O (4 mol%). aRecovered
starting material in parentheses.
Scheme 6 Reagents and conditions: (i) a) Na2SO3, H2O, D, b) POCl3, c)
NH3, CH3CN.
over, appeared to be relatively slow compared to that reported
8b
for the TA reaction of carbamate 1 (Scheme 1). In attempts to
further probe this observation, we performed the reactions for
fixed time periods (20 h and 40 h) (Scheme 7). When a 20 hour
reaction time was employed with the sulfamate ester 12, the
reaction proceeded well delivering the product in 53% isolated
yield. When this was extended to 40 hours, a small increase in
yield was observed (59%) suggesting that the rate of the reaction
slows over time. As a comparison the sulfonamide 22 gave only
35% of the isolated product 24 after 20 h, and 58% after 40 hours.
Scheme 4 Reagents and conditions: (i) PhI(OAc)2, MgO, CH2Cl2, 40 ◦C,
cat. Rh2(OAc)4; (ii) PhI(OAc)2, Al2O3, CH2Cl2, 40 ◦C, Rh2(OAc)4;
˚
(iii) PhIO, CH3CN, 3 A mol. sieves., cat. Cu(CH3CN)3PF6.
Results and discussion
Optimisation of the sulfamate ester TA reaction
Initial investigations
With these encouraging results in hand we proceeded to
investigate the effects of different amine ligands upon the yield
of the more synthetically interesting sulfamate ester TA reaction
(see Table 2). Each reaction was carried out as before but
the reaction time was kept to 3 days. Table 2 shows that the
optimum ligand was indeed EtN(iPr)2 (entry ii) as Donohoe
and co-workers found in the original TA reaction employing
The sulfamate ester substrates 12 and 20a–i were easily prepared
in generally excellent yields by reaction of the requisite homo-
allylic alcohol 19 with NH2SO2Cl, which is prepared simply
by reaction of chlorosulfonyl isocyanate with formic acid
(Table 1).14 Condensation with the alcohols was then carried
10a
out using pyridine as base in dichloromethane, or by simple
8b
carbamates (Scheme 1). Perhaps surprisingly, the reaction yield
reaction without base in DMA.15
was very similar when no amine ligand was added to the reaction
(entry i). Using one of Sharpless’ original aminohydroxylation
ligands, (DHQ)2PHAL, the yield was somewhat reduced and,
The sulfonamide 22 was prepared by reaction of 5-bromo-1-
pentene (21) with sodium sulfite, followed by sulfonyl chloride
formation, and finally reaction with ammonia (Scheme 6).17
Preliminary investigations into the tethered aminohydroxy-
lation reaction of the homo-allylic sulfamate esters and the
sulfonamides focused on the simplest systems 12 and 22
(Scheme 7). The optimum TA reaction conditions developed
by Donohoe and co-workers were initially employed.8 In this
way, treatment of sulfamate ester 12 or sulfonamide 22 with aq.
NaOH (0.92 equiv.) and tBuOCl (1 equiv.) in nPrOH to generate
the N-chloroamine intermediates was followed by addition of
EtN(iPr)2 (5 mol%) and potassium osmate (4 mol%) to produce
the oxathiazinane 23 and thiazinane 24, respectively. The highest
isolated product yield from the sulfamate ester 12 was obtained
after 7 days reaction time, when the reaction colour turned black
denoting end of turn-over of the osmium catalyst. This delivered
an isolated yield of 68% of the product 23, with 24% starting
material 12 recovered. In the case of sulfonamide 22, end of turn-
over came after 3 days reaction time, delivering 59% isolated
yield of the product 24, with 29% starting material recovered.
The rates of reaction of 12 and 22, as indicated by the time
taken for precipitation of osmium ‘black’ signifying end of turn-
8b
as Donohoe et al. had found, no enantiomeric induction was
observed in the reaction. The use of both quinuclidine (entry iv)
and DABCO (1,4-diazabicyclo[2.2.2]octane) (entry v) seemed to
retard the reaction.
Investigations into the scope of the sulfamate ester TA reaction
We next investigated the scope of the reaction by using differ-
ently substituted homo-allylic sulfamate esters 20a–i using the
optimised TA conditions (Table 3, entry i). Firstly, we established
that a single substituent at the 2-position was compatible with
the TA process, the 2-methyl and 2-methoxy analogues 20a and
20b giving good yields of the substituted oxathiazinane products
25 and 26, respectively (entries ii and iii). Disappointingly, no
diastereoselection was observed in either reaction, products
25 and 26 being obtained as separable 1 : 1 diastereomeric
mixtures. We anticipated that the 2,2-dimethylated analogue 20c,
by virtue of the Thorpe–Ingold effect, would cyclise efficiently
but unfortunately only trace quantities of oxathiazinane 27 were
observed (entry iv). C-1 substitution was examined next, the
Scheme 5
6 0 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1

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Table 1 Yields and conditions used for synthesis of sulfamate esters 12 and 20a–ia
Structure
Yield, Method
Structure
Yield, Method
92%, Method (i)
84%, Method (i)
73%, Method (i)
73%, Method (i)
78%, Method (ii)
—,16 Method (i)
94%, Method (i)
89%, Method (i)
75%, Method (ii)
81%, Method (i)
a Reagents and conditions: (i) NH2SO2Cl, dimethylacetamide (DMA); (ii) NH2SO2Cl, pyridine, CH2Cl2.
Scheme 7 Reagents and conditions: (i) nPrOH–H2O, NaOH (0.92 equiv.), tBuOCl (1.0 equiv.), EtN(iPr)2 (5 mol%), K2OsO4·2H2O (4 mol%).
aRecovered starting material in parentheses. b Denotes the end of turn-over.
ester 20d furnishing a reasonable yield of cyclised product 28
in a 4 : 1 diastereomeric ratio, with the syn-product shown
predominating (entry v). This is an interesting result, not only
due to the diastereoselectivity observed, but also because it is the
first successful TA reaction in which the substrate bears an ester
functionality (indicating that under these conditions the forma-
tion of the intermediate N-chloroamine salt, and the TA process
are faster than saponification). We next investigated the TA of C-
1 methyl analogue 20e: surprisingly, no cyclisation was observed
again demonstrating the unpredictably of this process (entry vi).
The presence of substituents on the alkene was investigated
next (entries vii–x). Substrates containing a terminal E-phenyl
group 20i, a terminal E-ethyl group 20g and a terminal Z-ethyl
group 20f all gave little or no cyclisation. Finally, substrate 20h,
containing a methyl substituent on the internal alkene site, was
prepared but again no TA reaction was observed (entry ix). It
therefore appears that the sulfamate TA process is limited to
monosubstituted alkenes, possibly for steric reasons.
Crystal structures were obtained of both diastereoisomers of
methoxy-substituted product 26 (Fig. 1).18 The crystal structures
show the conformation of both diastereoisomers to be classically
chair-like with the C-4 appended hydroxymethyl substituents
equatorially oriented in both diastereoisomers and the C-5
methoxy then taking either the axial or equatorial position.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1
6 0 5

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Table 2 Effect of ligand on TA reaction of sulfamate ester 12a
oxygen occupy 1,3-diaxial positions, i.e. syn-34a. An additional
factor deciding the outcome of the diastereoselectivities of the
these reactions could be the elongated nature of O–S and S–
N bonds, as discussed above, perhaps allowing the reactive
=
=
N Os O moiety to reach relatively unhindered to either
diastereomeric face of the olefin.
Entry
Amine ligand
Yield
Ring-opening reactions of 1,2,3-oxathiazinane products
i
no ligand
EtN(iPr)2
(DHQ)2PHAL
quinuclidine
DABCO
62% (18%)b
64% (20%)b
42% (26%)b
18% (63%)b
21% (65%)b
ii
iii
iv
v
In recent years 1,2,3-oxathiazinanes (cyclic sulfamidates) have
been used as the electrophilic participants in a range of
nucleophilic ring-opening reactions.13 We felt that the use of
this methodology in conjunction with the sulfamate ester TA
process would deliver useful new b-functionalised amino alcohol
building blocks. To illustrate this potential we briefly studied the
elaboration of the parent cyclic sulfamidate 23 (Scheme 9).
Treatment of the primary alcohol 23 with TBSCl/imidazole
followed by N-protection with CbzCl/tBuONa gave fully pro-
tected oxathiazinane 35. Reaction of N-Cbz oxathiazinane 35
with morpholine in acetonitrile led to attack at the sulfamidate
C-6 position, acidic hydrolysis (1 M HCl) of the subsequent
reaction mixture giving the ring-opened, silyl-deprotected prod-
uct 36 in 86% yield (Scheme 9). The ring-opening reaction
could also be carried out with phenylthiolate, hydrolysis of
the ensuing reaction mixture with 1 M aqueous KH2PO4 then
giving sulfide 37 in good yield. Finally, we were able to carry
out intramolecular nucleophilic ring-opening. Treatment of
the oxathiazinane 35 with TBAF gave 3-aminotetrahydrofuran
as its Cbz-sulfamic acid derivative 38 in reasonable yield,
presumably via desilylation and cyclisation of the intermediate
tetrabutylammonium alkoxide 39, as shown.
a Reagents and conditions: (i) nPrOH–H2O, NaOH (0.92 equiv.), tBuOCl
(1.0 equiv.), ligand (5 mol%), K2OsO4·2H2O (4 mol%), 3 days.
b Recovered starting material in parentheses.
These X-ray data were valuable when rationalising the di-
astereoselectivity observed in the TA reactions of 20a and 20b.
We invoked 6-membered chair-like transition states 33a,b and
34a,b (Scheme 8), resembling the conformations observed in the
crystal structures. In the case of the C-1 ester substituted example
20d, likely transition states 33a and 33b shown in Scheme 8,
indicate that diaxial [1,3]-strain between the ester substituent
and the axial sulfonyl oxygen in anti-33b is likely to favour syn-
33a and hence the production of syn-28a (formed in 80 : 20 dr).
No diastereoselectivity was observed with either C-2 substituted
substrate (20a or 20b), possibly due the lack of sufficient diaxial
[1,3]-strain in the proposed cyclic transition state, in which the
methoxy substituent and a lone pair of electrons on the ring
Table 3 Investigations into scope of the sulfamate ester TA processa
Entry
i
s.m.
Product
Yield, ratio
68% (24%)b
Entry
vi
s.m.
Product
Yield, ratio
—
12
20e
ii
20a
65% (21%),b 1 : 1c
vii
Z-20f
—
iii
iv
v
20b
20c
20d
67% (11%), b 1 : 1c
viii
ix
E-20g
20h
—
—
—
—
50% (28%), b 4 : 1c
x
20i
a Reagents and conditions: (i) nPrOH–H2O, NaOH (0.92 equiv.), tBuOCl (1.0 equiv.), EtN(iPr)2 (5 mol%), K2OsO4.2H2O (4 mol%). b Recovered
starting material in parenthesis. c Diastereomeric ratios were obtained from 1H NMR analysis of crude mixture.
6 0 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1

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Fig. 1 ORTEP drawing of compounds syn-26a and anti-26b (50% probability thermal ellipsoids).18
Scheme 8 Possible diastereomeric transition states.
Scheme 9 Reagents and conditions: (i) TBDMSCl, imdazole, DMF; (ii) tBuONa, CbzCl, DME; (iii) a) morpholine, CH3CN, b) 1 M HCl; (iv) a)
PhSH, K2CO3, CH3CN, b) 1 M KH2PO3; (v) TBAF, THF.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1
6 0 7

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2-Methyl-but-3-enyl sulfamate 20a. Prepared by means of
procedure A, using formic acid (0.33 ml, 8.72 mmol), chloro-
sulfonyl isocyanate (0.76 ml, 8.72 mmol), DMA (10 ml) and 2-
methyl-but-3-en-1-ol (0.6 ml, 5.81 mmol) gave the title compound
20a (696 mg, 73%) as a colourless oil; Rf 0.09 (2 : 1, petrol(bp
40–60 ◦C)–Et2O); mmax(film)/cm−1 3370, 3283, 2978, 1361, 1182,
979, 923; dH(400 MHz; CDCl3) 5.75 (1H, m, CH-3), 5.2–5.05
(2H, m, CH2-4), 4.81 (2H, br s, NH2), 4.10 (1H, dd, J 9.5,
6.5, CHAHB-1), 4.04 (1H, dd, J 9.5, 7, CHAHB-1), 2.63 (1H, m,
Conclusion
We have reported the first use of both homo-allylic sulfamate
esters and a sulfonamide in tethered aminohydroxylation (TA)
reactions, delivering good yields of certain cyclic sulfami-
date/thiazinane products. Investigations into the sulfamate ester
substrates showed that yields and diastereoselectivities of the
reactions were substrate dependent, and that further alkene
substitution does not appear to be compatible with the process.
We also studied elaboration of one of cyclic sulfamidate TA
products, showing that nucleophilic ring-opening reactions can
be used to prepare functionalised acyclic b-amino alcohols and
functionalised 3-aminotetrahydrofuran building blocks.
CH-2), 1.10 (3H, d, J 6.5, CH3); dC(100 MHz; CDCl3) 138.7,
+
116.2, 75.0, 37.1, 16.2; m/z (CI) 183.0809 (100%, M + NH4
,
C5H15N2O3S requires 183.0803), 86 (5) and 68 (25).
2-Methoxy-but-3-enyl sulfamate 20b. Prepared by means
of procedure B, using formic acid (0.19 ml, 5.08 mmol),
chlorosulfonyl isocyanate (0.44 ml, 5.08 mmol), 2-methoxy-but-
3-en-1-ol (345 mg, 3.38 mmol), pyridine (0.41 ml, 5.08 mmol)
and dichloromethane (10 ml) gave the title compound 20b
(476 mg, 78%) as a colourless oil; Rf 0.29 (1 : 3, petrol(bp 40–
60 ◦C)–Et2O); mmax(film)/cm−1 3364, 3278, 3096, 1369, 1182, 993;
dH(400 MHz; CDCl3) 5.70 (1H, m, CH-3), 5.46–5.35 (2H, m,
CH2-4), 5.08 (2H, br s, NH2), 4.25 (1H, m, CH-2), 4.19 (1H, dd,
J 10, 6.5, CHAHB-1), 3.94 (1H, m, CHAHB-1), 3.36 (3H, s, CH3);
dC(100 MHz; CDCl3) 132.9, 120.7, 80.6, 72.5, 56.8; m/z (CI)
199.0750 (100%, M + NH4+, C5H15N2O4S requires 199.0753),
182 (5, M + H+).
2,2-Dimethyl-but-3-enyl sulfamate 20c. Prepared by means
of procedure A. Due to the volatility of 2,2-dimethyl-but-3-
en-1-ol a yield of the product could not be obtained. Product
obtained as a colourless oil; Rf 0.22 (1 : 1, petrol(bp 40–60 ◦C)–
Et2O); mmax(film)/cm−1 3371, 3286, 2972, 1364, 1163, 976, 925,
834; dH(400 MHz; CDCl3) 5.81 (1H, dd, J 11, 17.5, CH-3), 5.15–
5.05 (2H, m, CH2-4), 4.67 (2H, br s, NH2), 3.95 (2H, s, CH2-1),
1.11 (6H, s, C(CH3)2); dC(100 MHz; CDCl3) 143.4, 113.7, 78.6,
37.5, 23.7; m/z (CI) 197.0957 (100%, M + NH4+, C6H17N2O3S
requires 197.0960), 115 (10), 88 (5), 82 (15).
Experimental
NMR spectra were recorded on a Jeol EX-270 or Jeol EX-400
instrument (specified below); chemical shifts are quoted in parts
per million (ppm) calibrated to residual non-deuterated solvent.
Infrared spectra were recorded on a ThermoNicolet IR100 spec-
trometer with NaCl plates. Chemical ionization (CI) and high
resolution mass spectra were recorded on a Micromass Autospec
spectrometer. Melting points were recorded on Gallenkamp
apparatus and are uncorrected. Thin layer chromatography was
performed on aluminium plates coated with Merck Silica gel 60
F254. Flash column chromatography was carried out using Fluka
flash silica gel 60 and the eluent is specified. Dichloromethane
was distilled from calcium hydride prior to use. Except where
specified, all reagents were purchased from commercial sources
and used without further purification.
Sulfamate esters (12, 20e, 20f, 20g and 20h)12 and the
sulfonamide (24)17 were prepared by literature procedures. All
homo-allylic alcohols were obtained from commercial sources
except; 2-methoxy-but-3-en-1-ol,19 2,2-dimethyl-but-3-en-1-ol,20
ethyl 2-hydroxy-pent-4-enoate21 and (E)-4-phenyl-but-3-en-1-
ol.22
Ethyl 2-sulfamoyloxy-pent-4-enoate 20d. Prepared by means
of procedure B, using formic acid (0.2 ml, 5.21 mmol), chloro-
sulfonyl isocyanate (0.45 ml, 5.21 mmol), 2-hydroxy-pent-4-
enoic acid ethyl ester (500 mg, 3.47 mmol), pyridine (0.42 ml,
5.21 mmol) and dichloromethane (10 ml) gave the title compound
20d (579 mg, 75%) as a colourless oil; Rf 0.32 (1 : 2, petrol(bp
40–60 ◦C)–Et2O); mmax(film)/cm−1 3370, 3282, 2986, 1742, 1377,
1187, 926; dH(400 MHz; CDCl3) 5.79 (1H, m, CH-3), 5.25–5.15
(4H, m, CH2-4, NH2), 5.01 (1H, dd, J 5, 7, CH-1), 4.35–4.2
(2H, m, CH2CH3), 2.75–2.6 (2H, m, CH2-2), 1.31 (3H, t, J 7,
CH2CH3); dC(100 MHz; CDCl3) 169.9, 130.9, 119.9, 79.2, 62.5,
36.2, 14.3; m/z (CI) 241.0858 (100%, M + NH4+, C7H17N2O5S
requires 241.0858) and 127 (10).
General procedure for synthesis of sulfamate esters
Procedure A: Formic acid (0.33 ml, 8.72 mmol, 1.5 equiv.) was
added dropwise to vigorously stirred, ice-cooled neat chlorosul-
fonyl isocyanate (0.76 ml, 8.72 mmol, 1.5 equiv., CAUTION:
gas evolved) under an atmosphere of Ar. The resulting viscous
solid/suspension was warmed to rt and stirred overnight. The
solid was dissolved in dry DMA (10 ml) at 0 ◦C, then stirred at
rt for a further 30 min. The homo-allylic alcohol (5.81 mmol, 1
equiv.) was added dropwise at 0 ◦C and stirring was continued
at rt for ∼4 h (consumption of starting material (s.m.) by TLC).
The reaction was partitioned between EtOAc (30 ml) and H2O
(20 ml). The aqueous phase was separated and extracted with
EtOAc (2 × 20 ml) and the combined organics washed with H2O
(2 × 20 ml) and brine (20 ml). The organics were dried (Na2SO4)
and evaporated under reduced pressure and the crude residue
was purified on silica gel.
Procedure B: Formic acid (0.19 ml, 5.08 mmol, 1.5 equiv.) was
added dropwise to vigorously stirred, ice-cooled neat chlorosul-
fonyl isocyanate (0.44 ml, 5.08 mmol, 1.5 equiv., CAUTION:
gas evolved) under an atmosphere of Ar. The resulting viscous
solid/suspension was warmed to rt and stirred overnight. The
solid was then dissolved in dry dichloromethane (8 ml) at 0 ◦C,
and stirred at rt for a further 30 min. A solution of homo-
allylic alcohol (3.38 mmol, 1 equiv.) and dry pyridine (0.41 ml,
5.08 mmol, 1.5 equiv.) in dry dichloromethane (2 ml) was then
added dropwise at 0 ◦C, then stirring was continued at rt for
∼3 h (consumption of s.m. by TLC). The reaction mixture
was partitioned between EtOAc (20 ml) and H2O (15 ml). The
aqueous phase was separated and extracted with EtOAc (2 ×
20 ml) and the combined organics were dried (Na2SO4) and
evaporated under reduced pressure. The crude residue was then
purified on silica gel.
(E)-4-Phenyl-but-3-enyl sulfamate 20i. Prepared by means
of procedure A, using formic acid (0.15 ml, 4.05 mmol),
chlorosulfonyl isocyanate (0.35 ml, 4.05 mmol), (E)-4-phenyl-
but-3-en-1-ol (400 mg, 2.70 mmol) and DMA (5 ml) gave the
title compound 20i (498 mg, 81%) as a cream coloured solid,
m.p. 8◦4–86 ◦C (from Et2O–petrol); Rf 0.15 (1 : 1 petrol(bp
40–60 C)–Et2O); mmax(film)/cm−1 3406, 3313, 1359, 1179, 968,
931; dH(400 MHz; CDCl3) 7.4–7.2 (5H, m, PhH), 6.52 (1H,
d, J 16, CH-4), 6.17 (1H, dt, J 16, 7, CH-3), 4.76 (2H, br s,
NH2), 4.64 (2H, t, J 7, CH2-1), 2.67 (2H, q, J 7, CH2-2);
dC(100 MHz; CDCl3) 136.7, 133.2, 128.4, 127.4, 126.0, 123.8,
70.3, 32.2; m/z (CI) 245.0962 (85%, M + NH4+, C10H17N2O3S
requires 245.0960), 148 (15), 131 (100), 115 (5).
General procedure for tethered aminohydroxylation (TA)
reactions23
An aqueous solution of NaOH (0.92 equiv., 0.08 M, kept a small
portion for later) was added to a stirred solution of sulfamate
ester or sulfonamide (1 equiv.) in nPrOH (12 ml mmol−1). After
6 0 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1

View Article Online
5 min, tBuOCl24 (1 equiv.) was added dropwise. After a further
5 min, the ligand (5 mol%) was added. Finally, to the reaction
was added K2OsO4·2H2O (4 mol%), dissolved in a small portion
of the aqueous 0.08 M NaOH solution prepared earlier. The
reaction was then stirred until the solution turned black, or until
a specified time, and then solid Na2SO3 (500 mg) was added to
the reaction. After ∼30 min, the reaction was extracted with
EtOAc (3×). The combined organics were filtered through a
plug of Na2SO4, and evaporated under reduced pressure. The
crude residue was then purified on silica gel.
1004, 910; m/z (CI) 199.0746 (100%, M + NH4+, C5H15N2O4S
requires 199.0753), 102 (5), 60 (10).
(5-Methoxy-2,2-dioxo-[1,2,3]oxathiazinan-4-yl)-methanol 26.
Prepared by means of the general TA procedure over 4 days,
using sulfamate ester 20b (105 mg, 0.58 mmol), nPrOH (7 ml),
NaOH (21 mg, 0.53 mmol), H2O (7 ml), tBuOCl (74 ll,
0.58 mmol), EtN(iPr)2 (5 ll, 29 lmol), K2OsO4·2H2O (9 mg,
23 lmol) gave recovered starting material (11 mg, 11%) along
with the title compound 26 (77 mg, 67%) as a mixture of 2 sep-
arable diastereoisomers. Characterisation of anti-4(RS),5(RS)
diastereoisomer: colourless cubic crystals, mp 118–119 ◦C (from
EtOAc–petrol(bp 40–60 ◦C)); Rf 0.27 (Et2O); mmax(film)/cm−1
3542, 3263, 1418, 1357, 1186, 979, 793; dH(400 MHz; d6-acetone)
6.26 (1H, br d, J 9, NH), 4.71 (1H, dd, J 4, 11.5, CHAHB-6), 4.35
(1H, dd, J 8, 11.5, CHAHB-6), 4.22 (1H, br s, OH), 3.89 (1H, dd,
J 11.5, 4.5, CHAHBOH), 3.76 (1H, dd, J 11.5, 6, CHAHBOH),
3.64 (1H, dt, J 4, 8, CH-5), 3.49 (1H, m, CH-4), 3.45 (3H, s,
OCH3); dC(100 MHz; d6-acetone) 71.5, 70.6, 61.0, 60.5, 58.2;
characterisation of syn-4(RS),5(SR) diastereoisomer: colourless
cubic crystals, mp 114–115 ◦C (from EtOAc–petrol(bp 40–
60 ◦C)); Rf 0.15 (Et2O); mmax(film)/cm−1 3267, 2925, 1431, 1360,
1186, 1035, 967, 791; dH(400 MHz; d6-acetone) 6.11 (1H, br
d, J 11, NH), 4.81 (1H, dd, J 13, 1.5, CHAHB-6), 4.59 (1H,
d, J 13, CHAHB-6), 4.05 (1H, m, CH-5), 3.86 (1H, m, CH-
4), 3.75 (1H, dt, J 11, 7.5, CHAHB-OH), 2.32 (1H, dt, J 11,
5, CHAHBOH), 3.48 (1H, br s, OH), 3.45 (3H, s, OCH3);
dC(100 MHz; d6-acetone) 72.8, 69.7, 61.6, 61.0, 57.0; m/z (CI)
215.0702 (100%, M + NH4+, C5H15N2O5S requires 215.0702),
91 (5), 58 (55).
(2,2-Dioxo-[1,2,3]oxathiazinan-4-yl)-methanol 23. Prepared
by means of the general TA procedure over 7 days, using
sulfamate ester 12 (500 mg, 3.31 mmol), nPrOH (40 ml),
NaOH (122 mg, 3.05 mmol), H2O (38 ml), tBuOCl (359 mg,
3.31 mmol), EtN(iPr)2 (29 ll, 0.166 mmol), K2OsO4·2H2O
(49 mg, 0.132 mmol) gave recovered starting material (121 mg,
24%) along with the title compound 23 (376 mg, 68%) as a
colourless viscous oil; Rf 0.20 (Et2O); mmax(film)/cm−1 3260, 1425,
1357, 1185, 1091, 1011, 785; dH(400 MHz; CDCl3) 4.76 (1H, dt,
J 2.5, 11.5, CHAHB-6), 4.62 (1H, ddd, J 11.5, 5, 1.5, CHAHB-6),
4.49 (1H, br d, J 7.5, NH), 3.9–3.8 (2H, m, CHAHBOH, CH-4),
3.75 (1H, m, CHAHBOH), 2.16 (1H, m, CHAHB-5), 1.67 (1H, t,
J 4.5, OH), 1.62 (1H, m, CHAHB-5); dC(100 MHz; d6-acetone)
+
73.8, 65.2, 59.5, 27.9; m/z (CI) 185.0594 (100%, M + NH4
,
C4H13N2O4S requires 185.0596), 88 (5), 56 (10).
(1,1-Dioxo-[1,2]thiazinan-3-yl)-methanol 24. Prepared by
means of the general TA procedure over 3 days, using sul-
fonamide 22 (140 mg, 0.94 mmol), nPrOH (11 ml), NaOH
(35 mg, 0.864 mmol), H2O (11 ml), tBuOCl (106 ll, 0.94 mmol),
EtN(iPr)2 (8 ll, 47 lmol), K2OsO4·2H2O (14 mg, 38 lmol) gave
recovered starting material (40 mg, 29%) along with the title
compound 24 (91 mg, 59%) as cubic colourless crystals, m.p.
101–102 ◦C (from EtOAc–petrol(bp 40–60 ◦C)); Rf 0.08 (Et2O);
mmax(film)/cm−1 3544, 3428, 3254, 1324, 1294, 1152; dH(400 MHz;
d6-acetone) 5.23 (1H, br s, NH), 4.01 (1H, br s, OH), 3.65–3.55
(2H, br m, CH2OH), 3.43 (1H, br m, CH-3), 3.09 (1H, dt, J 13.5,
3.5, CHAHB-6), 2.90 (1H, dt, J 4.5, 13.5, CHAHB-6), 2.22 (1H,
double quintet, J 14.5, 4, CHAHB-5), 2.11 (1H, m, CHAHB-5),
1.76 (1H, dq, J 14, 3, CHAHB-4), 1.48 (1H, dq, J 4, 14, CHAHB-
4); dC(100 MHz; d6-acetone) 65.0, 59.2, 49.7, 26.9, 23.7; m/z (CI)
183 (100%, M + NH4+), 166.0534 (45%, M + H+, C5H12NO3S
requires 166.0538), 134 (5), 70 (15).
4-Hydroxymethyl-2,2-dioxo-[1,2,3]oxathiazinane-6-carboxy-
lic acid ethyl ester 28. Prepared by means of the general TA
procedure over 2 days, using sulfamate ester 20d (114 mg,
0.51 mmol), nPrOH (6 ml), NaOH (19 mg, 0.47 mmol), H2O
(6 ml), tBuOCl (58 ll, 0.51 mmol), EtN(iPr)2 (5 ll, 26 lmol),
K2OsO4·2H2O (8 mg, 20 lmol) gave recovered starting material
(24 mg, 21%) along with the title compound 28 (61 mg, 50%) as a
4 : 1 mixture of diastereoisomers. Characterisation of the major
syn-4(SR),6(RS) diastereoisomer: colourless oil; Rf 0.26 (Et2O);
mmax(film)/cm−1 3529, 3261, 1744, 1372, 1191, 1102, 1046, 886,
829; dH(400 MHz; d6-acetone) 5.06 (1H, dd, J 12.5, 3, CH-6),
4.02 (2H, q, J 7.5, CH2CH3), 3.96 (1H, br s, NH), 3.25 (1H,
m, CH-4), 2.93 (1H, ddd, J 4, 6, 11, CHAHBOH), 2.73 (1H,
dt, J 11, 3.5, CHAHBOH), 3.22 (1H, dt, J 14, 12.5, CHAHB-5),
1.34 (1H, J 14, 3, CHAHB-5), 1.03 (3H, t, J 7.5, CH2CH3);
dC(100 MHz; d6-acetone) 167.0, 78.5, 63.1, 62.6, 55.5, 27.8, 14.0;
m/z (CI) 257.0808 (100%, M + NH4+, C7H17N2O6S requires
257.0807), 128 (15).
(5-Methyl-2,2-dioxo-[1,2,3]oxathiazinan-4-yl)-methanol 25.
Prepared by means of the general TA procedure over 3 days,
using sulfamate ester 20a (100 mg, 0.61 mmol), nPrOH
(7 ml), NaOH (22 mg, 0.56 mmol), H2O (7 ml), tBuOCl
(66 mg, 0.61 mmol), EtN(iPr)2 (5 ll, 30 lmol), K2OsO4·2H2O
(9 mg, 24 lmol) gave recovered starting material (21 mg,
21%) along with the title compound 25 (77 mg, 65%) as a
mixture of 2 separable diastereoisomers. Characterisation of
anti-4(SR),5(RS) diastereoisomer: colourless cubic crystals,
mp 138–139 ◦C (from EtOAc–petrol(bp 40–60 ◦C)); Rf 0.37
(Et2O); mmax(film)/cm−1 3542, 3263, 1418, 1357, 1186, 979,
793; dH(400 MHz; d6-acetone) 5.83 (1H, br d, J 9, NH), 4.55
(1H, dd, J 5, 11.5, CHAHB-6), 4.37 (1H, t, J 11.5, CHAHB-6),
4.24 (1H, t, J 5, OH), 3.96 (1H, dt, J 11.5, 4.5, CHAHBOH),
3.82 (1H, ddd, J 3, 6, 11.5, CHAHBOH), 3.46 (1H, m, CH-4),
2.30 (1H, m, CH-5), 1.05 (1H, d, J 7.5, CH3); dC(100 MHz;
d6-acetone) 3486, 3190, 1427, 1347, 1184, 1098; characterisation
of syn-4(SR),5(SR) diastereoisomer: colourless plate crystals,
mp 129–130 ◦C (from EtOAc–petrol(bp 40–60 ◦C)); Rf 0.27
(Et2O); mmax(film)/cm−1 3267, 2925, 1431, 1360, 1186, 1035,
967, 791; dH(400 MHz; d6-acetone) 6.30 (1H, br d, J 10, NH),
4.90 (1H, dd, J 2, 11.5, CHAHB-6), 4.48 (1H, dd, J 1.5, 11.5,
CHAHB-6), 4.20 (1H, t, J 6, OH), 4.04 (1H, m, CH-4), 3.85–3.7
(2H, m, CH2OH), 2.13 (1H, m, CH-5), 1.27 (3H, d, J 7.5,
CH3); dC(100 MHz; d6-acetone) 3563, 3134, 1462, 1355, 1188,
4-(tert-Butyldimethylsilanyloxymethyl)-2,2-dioxo-[1,2,3]ox-
athiazinane-3-carboxylic acid benzyl ester 35. a) Imidazole
(49 mg, 0.72 mmol), tert-butyldimethylchlorosilane (108 mg,
0.72 mmol) and (2,2-dioxo-[1,2,3]oxathiazinan-4-yl)-methanol
23 (100 mg, 0.60 mmol) were stirred in anhydrous dimethyl-
formamide (2 ml) under an atmosphere of Ar for 14 h. The
reaction was then diluted with Et2O (15 ml), then washed with
H2O (2 × 5 ml) and brine (10 ml). The organics were dried
(Na2SO4) and evaporated. The subsequent crude residue was
the purified on silica gel, eluting with Et2O–petrol(bp 40–60 ◦C)
2 : 1, delivering 4-(tert-butyldimethylsilanyloxymethyl)-[1,2,3]-
oxathiazinane 2,2-dioxide (160 mg, 95%) as a white solid;
mp 89–91 ◦C (from Et2O); Rf 0.30 (1 : 1, Et2O–petrol(bp
40–60 ◦C)); mmax(film)/cm−1 3266, 2925, 2856, 1405, 1363, 1119,
797; dH(400 MHz; CDCl3) 4.75 (1H, dt, J 2.5, 11.5, CHAHB-6),
4.57 (1H, ddd, J 11.5, 5, 1.5, CHAHB-6), 4.40 (1H, br d, J
10.5, NH), 3.85–3.75 (2H, m, CHAHBO, CH-4), 3.65 (1H,
dd, J 11, 2.5, CHAHBO), 2.16 (1H, m, CHAHB-5), 1.52 (1H,
m, CHAHB-5), 0.91 (9H, s, C(CH3)3), 0.08 (6H, s, Si(CH3)3);
dC(100 MHz; CDCl3) 71.6, 64.2, 56.4, 26.0, 25.6, 18.5, −4.37,
−5.41; m/z (CI) 299.1458 (100%, M + NH4+, C10H27N2O4SiS
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1
6 0 9

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requires 299.1461), 282 (30, M + H+), 224 (25, M − tBu), 116
(20).
(Tetrahydrofuran-3-yl)-carbamic acid benzyl ester sulfamic
acid 38. A solution of TBAF (0.17 ml, 0.17 mmol, 1 M in THF)
was added dropwise to a stirred solution of N-Cbz 35 (36 mg,
0.09 mmol). The reaction was stirred for 1 h, then diluted with
EtOAc (5 ml) and 1 M aqueous KH2PO4 (5 ml) and stirring was
continued for 1 h. The aqueous was then separated and extracted
with EtOAc (3 × 5 ml). The organics were dried (Na2SO4) and
evaporated and the subsequent crude residue was purified on
silica gel, eluting with Et2O–petrol(bp 40–60 ◦C) 2 : 1, delivering
the title compound 38 (16 mg, 62%) as a light yellow oil; Rf 0.16
b) A solution of 4-(tert-butyldimethylsilanyloxymethyl)-
[1,2,3]oxathiazinane 2,2-dioxide (100 mg, 0.36 mmol) in an-
hydrous DME (3 ml) was added dropwise to a solution of
sodium tert-butoxide (51 mg, 0.53 mmol) in anhydrous DME
(1 ml) under an atmosphere of Ar. The suspension was stirred
for 1.5 h then benzyl chloroformate (80 ll, 0.53 mmol) was
added dropwise and the reaction stirred for a further 14 h. The
reaction was the partitioned between EtOAc (10 ml) and H2O
(10 ml). After separation, the aqueous phase was dried (MgSO4)
and evaporated. The crude residue was then purified on silica
gel, eluting with Et2O–petrol(bp 40–60 ◦C) 1 : 1, delivering the
title compound 35 (133 mg, 90%) as a colourless oil; Rf 0.39
◦
(2 : 1, Et2O–petrol(bp 40–60 C)); mmax(film)/cm−1 3252, 1749,
1424, 1367, 1270, 1189, 783; dH(400 MHz; CDCl3) 7.45–7.35
(5H, m, ArH), 5.18 (2H, s, OCH2Ph), 4.86 (1H, m, CHAHB-5),
4.56 (1H, ddd, J 12, 5, 2, CHAHB-5), 4.50 (1H, br d, J 10.5,
OH), 4.30 (1H, dd, J 4, 11, CHAHB-2), 4.24 (1H, dd, J 3.5, 11,
CHAHB-2), 4.02 (1H, m, CH-3), 2.01 (1H, m, CHAHB-4), 1.67
(1H, dq, J 14.5, 2.5, CHAHB-4); dC(100 MHz; CDCl3) 154.7,
134.7, 129.1, 128.9, 128.6, 71.4, 70.6, 68.3, 54.6, 25.8; m/z (CI)
319.0974 (100%, M + NH4+, C12H19N2O6S requires 319.0964),
222 (10), 211 (25), 185 (5), 108 (25), 91 (10).
◦
(1 : 1, Et2O–petrol(bp 40–60 C)); mmax(film)/cm−1 2954, 2930,
2857, 1740, 1392, 1282, 1179, 839; dH(400 MHz; CDCl3) 7.5–7.3
(5H, m, ArH), 5.31 (2H, AB q, OCH2Ph), 4.75 (1H, dt, J 6,
11.5, CHAHB-6), 4.7–4.6 (2H, m, CHAHB-6, CH-4), 3.85–3.75
(2H, m, CH2O), 2.40 (1H, m, CHAHB-5), 2.27 (1H, m, CHAHB-
5), 0.87 (9H, s, C(CH3)3), 0.05 (6H, s, Si(CH3)2); dC(100 MHz;
CDCl3) 152.2, 134.8, 128.8, 128.6, 128.0, 70.3, 69.6, 61.6, 58.4,
25.9, 22.4, 18.3, −5.3, −5.4; m/z (CI) 433.1825 (100%, M +
NH4+, C18H33N2O6SiS requires 433.1829), 299 (20), 246 (20),
228 (15), 108 (45).
Acknowledgements
M.N.K thanks Elsevier for postdoctoral funding. We are grateful
to Dr. Adrian C. Whitwood for the X-ray crystallographic
studies.
(1-Hydroxymethyl-3-morpholin-4-yl-propyl)-carbamic
acid
benzyl ester 36. Morpholine (19 ll, 0.21 mmol) was added
to a solution of N-Cbz 35 (44 mg, 0.11 mmol) in acetonitrile
(1 ml) at rt under an atmosphere of Ar. The reaction was
stirred for 14 h then diluted with EtOAc (2 ml) and 1 M
aqueous HCl (2 ml). After stirring for 1 h, 2 M aqueous NaOH
(3 ml) was added and the mixture was extracted with EtOAc
(2 × 5 ml). The organics were dried (Na2SO4) and evaporated
and the crude residue was purified on silica gel, eluting with
EtOAc (10% MeOH), delivering the title compound 36 (28 mg,
86%) as a slightly yellow oil; Rf 0.21 (EtOAc (10% MeOH));
mmax(film)/cm−1 3316, 2955, 2857, 1697, 1538, 1252, 1162, 1069;
dH(270 MHz; CDCl3) 7.4–7.3 (5H, m, ArH), 5.77 (1H, br
d, J 10, NH), 5.08 (2H, br s, OCH2Ph), 3.9–3.5 (7H, br m,
CHN, CH2OH, 2 × OCH2CH2N), 2.7–2.2 (6H, br m, NCH2,
2 × OCH2CH2N), 1.90 (1H, m, CHAHBOH), 1.77 (1H, m,
CHAHBOH); dC(67.5 MHz; CDCl3) 156.2, 136.6, 128.6, 128.2,
128.1, 66.8, 66.6, 64.8, 53.7, 53.4, 51.4, 28.5; m/z (CI) 309.1816
(20%, M + H+, C16H25N2O2 requires 309.1814), 201 (100, M −
BnOH+), 100 (20).
References
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[1-(tert-Butyldimethylsilanyloxymethyl)-3-phenylsulfanylpro-
pyl]-carbamic acid benzyl ester 37. Thiophenol (26 ll,
0.25 mmol) and potassium carbonate (35 mg, 0.25 mmol) were
added to a stirred solution of N-Cbz 35 (46 mg, 0.11 mmol)
in acetonitrile (1 ml) at rt under an atmosphere of Ar. The
reaction was then diluted with EtOAc (3 ml) and 1 M aqueous
KH2PO4 (2 ml) then stirred for a further 20 h. The reaction was
then treated with 2 M aqueous NaOH (5 ml) and extracted with
EtOAc (10 ml). After separation, the aqueous was extracted
again with EtOAc (2 × 5 ml) then the combined organics were
dried (Na2SO4) and evaporated. The crude residue was then
purified on silica, eluting with Et2O–petrol(bp 40–60 ◦C) 1 : 3,
to give the title compound 37 (42 mg, 85%) as a light yellow oil;
Rf 0.28 (1 : 3, Et2O–petrol(bp 40–60 ◦C)); mmax(film)/cm−1 2952,
2928, 1701, 1526, 1255, 1063; dH(400 MHz; CDCl3) 7.4–7.1
(10H, m, PhH), 5.11 (2H, br s, OCH2Ph), 4.95 (1H, br d, J 8.5,
NH), 3.85 (1H, br m, CHN), 3.59 (2H, m, CH2O), 2.96 (2H, m,
SCH2), 1.85 (2H, m, CH2CH2CH2), 0.86 (9H, s, C(CH3)3), 0.02
(6H, s, Si(CH3)2); dC(100 MHz; CDCl3) 156.2, 136.7, 136.3,
134.9, 129.5, 129.0, 128.7, 128.3, 126.2, 22.9, 64.9, 52.0, 31.8,
30.6, 26.0, 18.4, −5.4; m/z (CI) 446.2177 (100%, M + H+,
C24H36NO3SiS requires 446.2185), 388 (20), 228 (15), 314 (10),
131 (10), 108 (10), 91 (30).
9 M. N. Kenworthy, G. D. McAllister and R. J. K. Taylor, Tetrahedron
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16 A yield could not be obtained from this reaction due to the volatility
of 2,2-dimethyl-but-3-en-1-ol.
17 P. Dauban and R. H. Dodd, Org. Lett., 2000, 2, 2327.
18 Crystal data for 26a: C5H11NO5S, M = 197.21, triclinic, a =
3
˚
˚
7.3712(5), b = 7.4301(5), c = 9.0586(6) A, V = 404.73(5) A , T =
115(2) K, space group P1, Z = 2, l(Mo-Ka) = 0.385 mm−1, 2291
¯
6 1 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1

View Article Online
reflections measured (Rint = 0.0149). The final R value was 0.0310 (all
20 (a) R. Na¨f-Mu¨ller, W. Pickenhagen and B. Willhalm, Helv. Chim.
Acta, 1981, 131, 1424; (b) P. Wipf and D. C. Aslan, J. Org. Chem.,
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1985, 50, 5334.
23 Adapted from a procedure developed by Donohoe et al., see ref. 8.
24 M. J. Mintz and C. Walling, Org. Synth., 1973, Coll. Vol. 5, 184.
data). Crystal data for 26b: C5H11NO5S, M = 197.21, monoclinic, a =
3
˚
˚
7.4175(4), b = 8.7683(5), c = 12.4464(7) A, V = 809.46(8) A , T =
115(2) K, space group P2(1)/n, Z = 4, l(Mo-Ka) = 0.385 mm−1
,
2345 reflections measured (Rint = 0.0239). The final R value was
0.0296 (all data). CCDC reference numbers 253422 (26a) and
253423 (26b). See http://www.rsc.org/suppdata/ob/b4/b416477f/
for crystallographic data in .cif or other electronic format.
19 P. D. Bartlett and S. D. Ross, J. Am. Chem. Soc., 1948, 70, 926.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 0 3 – 6 1 1
6 1 1